Just got myself 8 AAs (Rechargeable) from IKEA for my custom 9,6 V battery pack which I use for my Nikko Super Cruiser. A bit overkill when you count the capacity lol. :
Nikko 6.0v Ni-Cd battery cassette
NIKKO 6.0V 650mAh Ni-Cd SLOT IN BATTERY PACK AND 4 HOUR CHARGER | eBay
nikko ni-mh battery pack 6.0v in WV6 Wolverhampton for £15.00 for sale | Shpock
Nikko / Eztec 6 volt battery adaptor diy - YouTube